Basic shopping cart

Hi, I would like to setup a basic shopping cart based on the selections made at this site. [login to view URL] Firstly the customer selects what modem type: If the customer selects a PCMCIA or Desktop Modem, the modem price, the setup fee and delivery cost is added to the cart in step 4. If however they select the BYO modem, then they only pay for the Setup fee but must add the UTID number in the box provided. The customer must then complete step 5 (validation required)...Once the agreed to Terms and condition button is selected, the information in step 5 is emailed to me while the customer is then directed to the paypal subscribition section. Here is where the initial price is entered and were the monthly amounts is setup Currently i am using a simular function here: [login to view URL] For details on the Paypal subscribition string, please visit here: [login to view URL] page 47. Regards mike